Those installations, which were constructed by the U.S. military on remote Arctictundra beginning in 1954, were manned around the clock by U.S. and Canadian military personnel as an extension of the North American Air Defense Command (NORAD). The DEW Line was coordinated with several similar radar detection networks, such as the Pinetree Early Warning Line (which spanned the width of southern Canada near the 49th parallel), the Mid-Canada Line (which spanned the width of Canada at the 55th parallel), and the U.S. Navy’s Atlantic and Pacific Barrier, as well as air and sea patrols and radar stations in Iceland, Great Britain, the Faroe Islands in the North Atlantic, and Greenland. The first phase of the DEW Line became operational on July 31, 1957, and the line was expanded to encapsulate the Aleutian Islands and Greenland by 1961.

The DEW Line and other early-warning installations were effective deterrents against Soviet aggression during the Cold War. The Soviets knew that any air strike launched by them would be detected early enough that the U.S. Air Force could destroy most of their incoming bombers or ICBMs with fighter interceptors. The Soviets also knew that they would suffer considerable retaliation by the U.S. Strategic Air Command, whose airborne nuclear-armed bombers could be expected to survive the first strike.

The DEW Line grew out of a study in the early 1950s by scientists at the Massachusetts Institute of Technology (MIT), who found that the United States and Canada were vulnerable to a Soviet air attack from across the North Pole. The U.S. communications company Western Electric, which was controlled by AT&T, was awarded the contract to facilitate construction of the line. More than 25,000 workers, many of them subcontractors, built radar sites, roads, towers, airplane hangars, residences, and antennas in the most sparsely populated region of North America.

By the mid-1980s, aging facilities, improved technologies (such as the Airborne Warning and Control System [AWACS]), and advanced detection systems, together with the diminished threat of Soviet aggression in the waning years of the Cold War, led to the demise of older early-warning systems such as the DEW Line. Starting in 1985, the DEW Line system was replaced by the North Warning System, and many of the original DEW Line sites were abandoned or dismantled.

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